Background: There are times during endoscopic procedures when the surgeon has to operate ahead of the camera/telescope assembly. As a result, the image displayed on the monitor will be an inverted mirror image of the operative field (reverse alignment). The present study addresses the extent of these difficulties and suggests some techniques that may be used to overcome the problem.
Methods: Eight specialist registrars participated in experiments involving the execution of a simulated dissection task under 12 different imaging conditions. These conditions included normal alignment, reverse alignment, total or partial digital correction of reverse alignment (about the horizontal and vertical axes independently and together), and a simple rotation of the camera through 180 degrees. Normal, reverse, and corrected reverse alignment were also tested with optical axes of 45 degrees and 60 degrees. The endpoints were the task execution and the errors rate.
Results: A marked deterioration in execution time was observed when the surgeons worked under reverse alignment rather than under normal viewing (p = 0.036). Significant improvement in execution-time errors rate was found when both the horizontal and vertical axes were digitally corrected simultaneously (p = 0.27) and when the camera was rotated 180 degrees with respect to the telescope during reverse alignment (p = 0.28).
Conclusions: The effect on performance produced by reverse alignment of the endoscope and instruments can be overcome by means of digital electronic processing, or simply by turning the camera through 180 degrees.